Thermocouple and its electrical connection



'I Nov. 15, 1932. 4F. F. UEHLING 1387327 THERMOCOUPLE AND ITS ELECTRICALCONNECTION Filed March 22. 1929 2 Sheets-Sheet 1 i Za 5 4& 74

Nov. 15, 1932. F. F. UEHLING 9 3 THERMOCOUPLE AND ITS ELECTRICALCONNECTION Filed March 22, 1929 2 Sheets-Sheet 2 I Pate-med Nov. 15,1932 FBITZ UEHIING, OF IPASSAIC, NEW JERSEY TEEBMOGOUPLE AND ITSELECTBICAL CONNECYION Application filed March 22, 1929. SerialNo.'349.188.

My invention relates to aspecially designed thermo-junction for use 'incombination with an indicating galvanometer and a novel recording'galvanometer for recording the flow 5' of current from a thermo-couple,the details of which galvanometer are fully described in m prior patent,Number 1,727 ,494.

n the particular recording galvanometer referred to the pen mechanism isactuated by a circuit, part of the current through which isintermittently shunted .through the galvanometer and the'thermo-junction. The purpose of this invention is therefore to providea circuit which includes the thermojunction and an indicatinggalvanometer, the electric flow V through which is dependent upon theelectro-motive force of the junction, and is independent of any efl'ectdue to the electric flow through the circuit which includes the samecouple and the recording galvanometer.

Figure 1 illustrates the thermo-junction electrically connected with therecording galvanometer and the indicating galvanometer.

Figure 2 illustrates the therno-junction and a protecting tube therefor,the latter in cross section.

Figures 3 and 4 illustrate a special form of the thermo-junction, Figure4 being an end View of Figure 3.

Figure 5 illustrates a thermo-junction with eight leads, the fourpositive leads are shown stippled while the four negative leads of whichare shown plain.

Figure 6 shows another design of thermojunction with four independentnegative leads and four independent-positive leads constituting fourpairs of leads, each pair included in a circuit entirely independent ofthe remaining pairs of leads.

Inthe recording galvanometer described in my prior patent, Number 1,727,494, there is a resistance which is included in the circuit with thethermo-couple and the galvanometer. The same resistance is also includedin one or more independent circuits which do not include thegalvanometer or the thermocouple. It therefore follows that an electricflow through any one of the independent circuits would cause a dropacross the resistance which drop would afl'ect the flow through thegalvanometer as caused by the couple. This condition is essential tothesatisfactory operation of this particular type of recordinggalvanometer. On the other hand if an indicating galvanomter wereconnected with the same couple in'the usual way, it too would bedeflected in one direction or another independently of theelectro-motive force of the couple, as caused by the drop across the re-60 sistance in the mamer alreadyrefe'rred to. In order to eliminate thisefiect on an indicating galvanometer when used in conjunction with sucha recording galvanonieter, I

rovide a thermo-junction of the novel form GB erein described. s v Arecording galvanometer 6, Figure 1, is of the type described in theprior patent referred to, and is connected to measure the pelectro-motive force from a junction 5,Figure 2, which junction islocated in a protecting tube or casing 14. An indicating galvanometer 7,Figure 1, is connected to measure the electro-motive force from the samejunction. The junction may consist of two wires of differentcomposition, twisted or welded to-' gether to form a thermo-j unctionwhich upon the application of heat will 'create an electromotive force.The two wires of the particui lar thermo-junction referred 'to are'socon- 30 nected that the two ends of each wire,--1a and 2a, and 35 and 46respectively, Figure 2, j will extend from the junction to form twoindependent pairs'of leads, one pair, la and 36, for the recordinggalvanometer 6 and thefiother pair, 2a and 46, for the indicatinggalvanometer 7 The circuit which-includes the thermo-junction 5, leadsla and %and g the recording galvanometer 6 is therefore quiteindependent of the circuitwhich includes the thermo-junction, the leads2a and 4b and the indicating galvanometer 7. It therefore follows thatany flow through the circuit which includes the recording gal- 5'vanometer and which may be quite independent of the flow caused by thejunction (as described in my prior patent) will in no way afl'ect theflow through the circuit which includes the indicating galvanometer,said flow being entirely dependent upon the elec tre-motive force of thejunction itself.

A thermo-j unction with four leads as above described may be arranged ina multiplicity of ways, one which has particular merit is illustrated inFigures 3 and 4. The four ends of the two wires which are joined at agiven point to form the junction extend through four small holes orchannels 8, 9, 10 and 11, through the length of a piece of porcelain orother insulating material 12 as illustrated. The couple orjunction 5 isthus held in a fixed position at the end of the porcelain and may, ifdesired, be protected by cover not shown.

Although this thermo-junction is primarily designed to facilitate theuse of an indicating galvanometer in combination with the particulartype of recording galvanometer above referred to, it is obvious that afour poled junction of this kind may have numerous other applications inwhich the junction forms part of two circuits, the flow through each ofwhich being quite independent of the flow through the other. Furthermoreit is obvious that although I have llustrated, in Figure 2, a junctionwith only four leads, any number of leads may extend from the couple soas to provide a multiplicity of circuits, one independent of the otheras illustrated in Figures 5 and 6.

The thermo-junction as illustrated in Figure 5 consists, for example, oftwo positive thermo-couple elements, each element being in the form of awire, and two negative elements, said negative elements being also inthe form of a wire. These wires are twisted together in a region betweentheir extremities as illustrated, thereby providing a thermojunctionwith four negative and four positive leads, each lead extending directlyfrom the junction itself. Each air of leads may be included in anindepen ent circuit. The current flowing through any one pair or more ofthe leads may be influenced by external means without in any wayaffecting the current flowing through any of the remaining pairs ofleads. The obvious reason for the independence of the current flowingthrough any one pair of leads lies in the fact that none of the otherleads in any way form part of the circuit through said pair of leads.

Another form of thermo-junction which perhaps more clearlyillustratesthe purpose element of this junction is represented by a and the otherelement by b. It is obvious that the electro-motive force of thejunction may be measured by the indicating galvanometer simultaneouslythis electro-motiveforce may be graphically recorded by the recordinggalvanometer 6 when connected with the elements a and Z through theleads la and 31). Furthermore another circuit which includes 7 throughthe leads Qa and 41) and that the thermojunction may also include inthat' circuit means for changing the flow through the circuit, as forexample, a transformer 22 which, as illustrated, is connected with thejunction through leads 6a and 8b. The primary coil of the transformermay be connected with some source of alternating current therebyinducing an alternating current in the secondary coil of the transformerwhich is included in the circuit with the leads Ba and 8b. The point ofimportance is that any change in the current flow through the circuitwhich includes the' leads 6a and 8b as caused by the transformer 22 willin no way create any measurable influence on the remaining circuitswhich include the 'unction. Sinilariy a fourth circuit whic includes abattery 21 and an adjustable rheostat 20 which are connected with thecouple through leads 50, and 7 b will also have no measurable efiect onthe deflection of the indicating galvanometer 7. In other words theadjustable rheostat 20 may be adjust'ed from one extreme to the otherwhile simultaneously the indicating galvanometer? will measure the trueelectro-motive force as created by the junction alone. i

As previously stated and as described in my prior patent above referredto, the cur- *rent which flows through a circuit which includes thegalvanometer and the thermojunction in said patent is spasmodicallyinfluenced by the auxiliary circuit which insures contact between theneedle of the galvanometer and its respective contact points as coveredby said patent. In other words, as previously stated, without athermo-junction as herein described, an indicating galvanometer couldnot be used in conjunction with that particular type of recorderdescribed in said patent.

Although :the herein described junc'tion was particularly designed tosimultaneously actuate an indicating galvanometer and the particularrecording galvanometer described in my prior patent, it is obvious thatit may have many applications where influences other than that of thetemperature of the junction maybe brought to bear on one or more of the.ircuits which include the junetion.

Having ths described my invention what u I claim as new between theirrespective ends, an electric circuit which includes the junction, thatpart of p and desire 'to secure by Letters; Patent is: I of ths nventonis shown n Fgure 6. One

the first wire between the junction and one of its ends, and that partof the second wire between the junction and one of its ends, and a.second circuitwhich includes the junction, that part ofthe first wirebetween the junction and the other of its end's, and that part of thesecond wire between the junction and the other of its ends.

2. In a device of the class described, the combination with a piece ofmetal, of a second piece of metal, a thermo-'unction formed by fasteningthe two pieces o metal together, an electrical conductor from the firstpiece of metal, a second electrical conductor from the rst piece ofmetal, a third electrical conductor from the second piece of metal, afourth electrical conductor :from the second piece of metal, an electriccircuit which includes the junction, the first conductor and the thirdconductor, and a second electric circuit which includes the junction,the second conductor and the fourth conductor.

3. In a device of the class described, the combination with athermo-junction, of a. multiplicity of positive leads from the junction,a multiplicity of negative leads from the junction, and a multiplicityof electric circuits each of which includes the junction and a pair ofleads.

4. A method for including a single thermojunction in each of amultiplicity of electric circuits so that the efi'ect on the flowthrough any one of the circuits, as caused' by an means other than thejunction, will not afl'ect the flow through the other circuits, saidmethod consistin in connecting the junction into each circuit %y meansof a separate lead from the positive pole of the junction and a separatelead from the negative pole of the junction.

5. In a device of the class described, the combination with amultiplicity of wires of a given composition, of a multiplicity of wiresof a different composition, an electrical connection through all of thewires at a point between their respective ends, and a multiplicity ofcircuits each including the electrical connection, and one end of one ofthe wires of one composition, and one end of one of the wires of theother composition.

FRITZ FREDERICK UEHLIN G.

